1. Field of the invention
The present invention relates to an improved method and apparatus for levelling suspended ceiling grid systems.
2. Description of the Prior Art
Suspended ceiling systems are well known and are the most common ceiling system used in office complexes and residential basement renovations. The suspended ceiling grid system comprises wall angle mouldings, main grid members (main tees) running in one direction of the ceiling with cross members (cross tees) connected to adjacent main grid members to form the grid pattern. The most common grid patterns are rectilinear or square grids although a non-rectilinear pattern can be used if desired.
In installing a suspended ceiling system the first step after doing a layout is the installation of the wall angle moulding. Typically a mark is made at the height desired for the new ceiling. The height of the wall angle moulding is added and by using a carpenter's level a level line is marked around three walls. A chalk line can be used to mark the fourth wall. The wall angle moulding is then fastened to the wall with the top edge of the moulding placed on the level line. Making sure the wall angle moulding is at the same height and level around the room is an important first step in installing the ceiling properly.
The main grid members or tees are suspended from the floor above by wire or plastic fasteners. With reference to the layout, the distance from one wall for the border panels is measured. Using that distance and a chalk line the location of the first main tee is marked on the floor joists. Chalk lines are then made parallel to the first chalk line the length of a panel (typically four feet). Wire or plastic fasteners are then nailed or screwed into the floor joists (or floor) approximately every four feet along the chalk lines. Hanger wires are then securely attached to the fasteners.
Very seldom is a room perfectly square. So from any corner of the room, two reference strings are stretched along both walls at the distance calculated for the border panels. The strings are attached to the bottom of the wall angle moulding by nails, pins or tape and aligned so they intersect at a 90.degree. angle. This will insure that the grid pattern is square. One string will be the guide for the first main tee and the other string for the first row of cross tees.
The first main tee is trimmed so that a cross tee slot lines up with the cross tee guide string when the trimmed end is set on the end wall moulding. The trimmed main tee may then be placed on the side wall moulding with the trimmed end against the end wall. A mark is made on the side wall through the wire support hole in the main tee that is farthest from the end wall but closest to a hanger wire. The process is repeated on the opposite wall. A tight string line is stretched across the room from mark to mark. The hanger wires are bent at 90.degree. where they touch the string. Additional strings are utilized at eight to ten foot intervals and hanger wires bent so that the ceiling will be level across the room.
The first main tee is installed at the guide string with the trimmed end on the end wall moulding and the other end supported by one of the pre-bent hanger wires. To span the length of the room main tees are connected until the last main tee needs trimming to fit on the opposite end wall moulding. The main tees are supported every eight to ten feet using the pre-bent hanger wires. The remaining hanging wires are inserted into the support holes in the main tee. Using a level the wires are adjusted to ensure the main tee is level. The process is repeated for each row of main tees.
Starting at the guide string the cross tees are installed between main tees and for some grid systems (2'.times.2') between cross tees. The middle ceiling panels are inserted into place to square up the grid. The main tee is then realigned with the guide string as the grid structure with panels inserted will slide along the wall angle moulding. The cross tees between the main tees and wall angle moulding are then measured, trimmed and installed starting at the guide string, doing first a cross tee on one side then the opposite side of the room alternately until all cross tees are in place.
The ceiling panels are then installed starting first with the middle panels and then the panels around the border of the room that must be measured and cut to fit the openings.